A DNS study of extreme and leading points in lean hydrogen-air turbulent flames-Part I: Local thermochemical structure and reaction rates

Lee, HsuChew1,2; Dai, Peng1; Wan, Minping1,2; Lipatnikov, Andrei N.3

2022

10.1016/j.combustflame.2021.111716

COMBUSTION AND FLAME   影响因子和分区

0010-2180

1556-2921

A Direct Numerical Simulation (DNS) study of statistically one-dimensional and planar, lean complexchemistry hydrogen-air flames characterized by a low Lewis number Le and three different Karlovitz numbers Ka ranging from 3 to 33 is performed, with the same complex-chemistry flames being also simulated by setting molecular diffusivities of all species equal to the heat diffusivity of the mixture. The simulations predict a significant increase in a ratio of turbulent burning velocity to the laminar flame speed in the former ( Le < 1 ) flames when compared to the latter (equidiffusive) flames. Extreme points characterized by the peak (over the computational domain) Fuel Consumption Rate (FCR) or Heat Release Rate (HRR) are found at each instant. In the equidiffusive flames, such extreme FCR and HRR are close to their peak values in the unperturbed laminar flame. If Le is low, the former rates are significantly higher than the latter ones due to an increase in the local temperature, equivalence ratio, and radical mass fractions, caused by diffusive-thermal effects. While the studied extreme points may appear sufficiently far from the leading edge of the instantaneous flame brush, leading points characterized by a lower, but still high ( Le < 1 ) FCR or HRR are observed close to the leading edge at each instant. Various local characteristics (temperature, equivalence ratio, species mass fractions and their gradients, reaction rates, etc.) of the extreme and leading points are explored and significant differences between zones characterized by high FCR or HRR are revealed. For instance, in the latter zones, major chemical pathways are changed. Moreover, while the extreme HRRs strongly fluctuate in time, with their mean and rms values being significantly increased by Ka , the extreme FCRs fluctuate weakly and are close at different Ka , thus, im plying that almost the same extreme FCR can be reached in substantially different local burning structures. (c) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Hydrogen DNS Turbulent combustion Lewis number Turbulent consumption speed Diffusive-thermal effects Leading point concept

SCI ; EI

英语

第一 ; 通讯

NSFC[91752201,51976088] ; Shenzhen Science and Technology Program[KQTD20180411143441009] ; Department of Science and Technology of Guangdong Province["2019B21203001","2020B1212030001"] ; Joint Program of Shenzhen Clean Energy Research Institute[LCH2019011] ; SUSTech[CERI-KY-2019-003]

Thermodynamics ; Energy & Fuels ; Engineering

Thermodynamics ; Energy & Fuels ; Engineering, Multidisciplinary ; Engineering, Chemical ; Engineering, Mechanical

WOS:000735767500004

ELSEVIER SCIENCE INC

20213710890823

Air ; Combustion ; Reaction rates

Chemical Reactions:802.2 ; Chemical Products Generally:804

ENGINEERING

Web of Science

1.Southern Univ Sci & Technol, Dept Mech & Aerosp Engn, Guangdong Prov Key Lab Turbulence Res & Applicat, Shenzhen 518055, Peoples R China
2.Southern Univ Sci & Technol, Guangdong Hong Kong Macao Joint Lab Data Driven F, Shenzhen 518055, Peoples R China
3.Chalmers Univ Technol, Dept Mech & Maritime Sci, SE-41296 Gothenburg, Sweden

Lee, HsuChew,Dai, Peng,Wan, Minping,et al. A DNS study of extreme and leading points in lean hydrogen-air turbulent flames-Part I: Local thermochemical structure and reaction rates[J]. COMBUSTION AND FLAME,2022,235.

Lee, HsuChew,Dai, Peng,Wan, Minping,&Lipatnikov, Andrei N..(2022).A DNS study of extreme and leading points in lean hydrogen-air turbulent flames-Part I: Local thermochemical structure and reaction rates.COMBUSTION AND FLAME,235.

Lee, HsuChew,et al."A DNS study of extreme and leading points in lean hydrogen-air turbulent flames-Part I: Local thermochemical structure and reaction rates".COMBUSTION AND FLAME 235(2022).